A Closed-Loop Current Source Gate Driver With Active Gate Current Control for Dynamic Voltage Balancing in Series-Connected GaN HEMTs

In this study, a novel closed-loop current source gate driver is presented to address the unbalanced dynamic voltage sharing issue. Additional compensation current is actively injected into the switch gate to counteract the voltage imbalance brought by the device-to-ground displacement currents. Compared with the conventional voltage source gate driver-based active gate control method, the proposed current source gate driver tunes the switch turn-off timing and dv/dt more accurately, because the switch gate current is directly regulated. Meanwhile, since both of the pulse width and amplitude of the compensation gate current can be adjusted, the proposed active gate control is more flexible for adapting to different operating conditions. Moreover, without employing snubber circuits or extra Miller capacitors, the switching speed and switching energy of the GaN devices are not compromised. By implementing the proposed gate driver and voltage balancing schemes, well-balanced voltage sharing can be obtained for both soft-switching and hard-switching scenarios. A series-connected GaN-based multiple pulse tester (MPT) is built to prove the effectiveness of the proposed approach under different load and different switching speed (dv/dt) conditions.